Project Summary/Abstract: Synthesis and Studies of a New Family of Antibiotics Antibiotic-resistant bacteria cause more than 2 million illnesses and more than 23,000 deaths in the US each year, with direct overall societal costs of about $20 billion and additional indirect societal costs of about $35 billion due to lost productivity. Although there is a desperate need for new antibiotics to fight the growing threat of antibiotic-resistant bacteria, the development of new antibiotics has dropped to a trickle. If effective new antibiotics are not developed, many more people will be sickened and die, at great human and financial cost. At the beginning of 2015 a new peptide antibiotic was reported, with great attention in both the scientific press and the popular press. The antibiotic, teixobactin is a non-ribosomal undecapeptide containing a macrocyclic depsipeptide group and the arginine analogue enduracididine or allo-enduracididine. Teixobactin has generated considerable excitement because it kills gram-positive bacteria without detectable resistance and is effective against bacteria that are resistant to other antibiotics. Pathogens against which teixobactin is active include Staphylococcus aureus, Streptococcus pneumoniae and other Streptococci, Bacillus anthracis, and Mycobacterium tuberculosis -- the pathogens that cause staph infections, bacterial pneumonia, anthrax, and tuberculosis. Teixobactin is effective against bacteria that have developed resistance to other antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). Teixobactin is also effective against Clostridium difficile, which has become a particular problem as a result of other antibiotics. If teixobactin or teixobactin analogues realize their promise, they will change clinical practice for the treatment of antibiotic-resistant infections. Understanding the teixobactin pharmacophore and having access teixobactin and analogues is essential to realizing this promise. This proposal seeks to elucidate the pharmacophore of teixobactin, develop a synthesis of teixobactin, and discover simpler analogues with similar pharmacological properties. The working hypotheses behind this work are that a biomimetic synthesis of teixobactin is possible, that the pharmacophore is embodied primarily in the macrocyclic region of the molecule, and that simpler analogues derived from this region will have comparable pharmacological properties. In executing this project, the PI and his research group will develop a synthetic route that permits the creation of teixobactin and analogues. They will develop an efficient synthesis of protected enduracididine stereoisomers suitable for use in Fmoc-based solid-phase peptide synthesis. They will assess the activity of the teixobactin analogues against gram-positive bacteria and compare them to teixobactin. They will prepare and study derivatives of teixobactin to elucidate the teixobactin pharmacophore. The outcome of these studies will be a better understanding of the teixobactin pharmacophore and synthetic access to building blocks, teixobactin, and teixobactin analogues.